Abstract

PM10 samples were collected from Huangshi (HS) city, Central China during April 2012 to March 2013, and were analyzed for short-chain saturated dicarboxylic acids (diacids) using a capillary gas chromatograph (GC). We found that oxalic acid (C2, 318 ± 104 ng·m−3) was the most abundant diacid species, followed by malonic acid (C3, 25.4 ± 9.11 ng·m−3) and succinic acid (C4, 2.09 ± 0.52 ng·m−3). The concentrations of C2 and C4 diacids were highest in winter, followed by summer and spring, and lowest in autumn. C3 diacid was decreased in the order of summer > winter > autumn > spring. Further, the seasonal variations of WSOC (water-soluble organic carbon)- and OC (organic carbon)-normalized diacid concentrations were similar to those of diacid concentrations, suggesting that both primary emission and secondary production are important sources for diacids in Huangshi (HS) aerosols. Strong correlations were found among C2 diacid and the three ions SO42−, NO3−, and NH4+ in summer and winter, suggesting that the species could undergo a similar secondary oxidation processing. C2 had good correlation with K+ in summer and autumn, which indicates an enhanced contribution of combustion sources for C2 diacid. Moreover, according to the ratio of C2/K+, we can conclude that C2 diacid should be formed by a secondary reaction of biomass combustion in HS aerosols, especially in summer and autumn. The ratios of C2/C4 and C3/C4 were compared with those reported in other sites, and the results suggest that HS aerosols should be more photochemically aged than at other urban areas. Principal component analysis of diacids and selected water-soluble inorganic ions over four seasons suggests that HS aerosols are influenced not only from primary emission, but also from secondary reaction. According to the linear relation between C2 and C3 diacids, the results indicate that C2 diacid is formed from the oxidation of hydrocarbon compounds in spring, while it is from the oxidation of C3 and C4 diacids in summer, autumn, and winter.
View Full-Text

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited